There are two ways to remove pages from a space. You can either archive or delete them.
Archive a Page
If you are able to archive pages in your instance you can use the page menu to do this.
Hover over the name of the page you want to move to reveal the page menu. Select the menu icon then Archive.
A confirmation message appears. Select Apply to archive the page.
Delete a Page
You can delete a page from the page menu.
Hover over the name of the page you want to move to reveal the page menu. Select the menu icon then Delete.
A confirmation message appears. Select Apply to delete the page.